Dextran (C.sub.6 H.sub.10 O.sub.5).sub.n is a polysaccharide polymer containing a plurality of mainly alpha-1,6 linked glucopyranose of glycosyl units obtained by the action of certain organisms upon sucrose by methods well known to the prior art. It is generally produced in the form of a polydispersed molecule of a mixture of polymers of various molecular weights.
Iron dextran has been developed and utilized as a satisfactory product for therapeutic use, primarily as an agent for correcting iron deficiencies in animals and humans by parenteral administration as by intravenous or intramuscular injection. This product has certain advantages deriving from low toxicity, low incidence of side reactions and effective rate of iron absorption. It is frequently prepared by forming a complex of dextran with colloidal ferric hydroxide.
Certain prior art patents describe ferric hydroxide complexes with dextran or other carbohydrate derivatives in efforts to achieve a desired high iron content and suitable stability and low toxicity. Illustrative of such art are U.S. Pat. No. 3,536,696 to Alsop and Bremner and British Pat. No. 1,200,902 to the same inventors. Their U.S. patent describes the formation of ferric hydroxide complexes with a dextran monocarboxylic acid formed by introducing a carboxylic acid group into a terminal unit of the dextran polymer to form a dextran heptonic acid. The Alsop et al. British patent relates to a procedure for forming the ferric hydroxide complex by controlling the rate of addition of alkali during complexing. No reference is made to the use of any type of dextran polycarboxylic acid.
A patent to Dahlberg et al., U.S. Pat. No. 3,928,581, states that the use of low molecular weight dextrans and dextrans in the formation of iron complexes is undesirable due to toxic and other side effects and proposes instead to utilize certain more complex polymers formed from a saccharide such as sucrose, a polymerization agent such as an epoxide, and a hexitol such as sorbitol, and then reacting with cyanide followed by acidification and hydrolysis to form an end product having a carboxylic acid group attached thereto.
Certain other prior art patents describe oxidation with various types of carbohydrate polymers to form products useful in industry, such as tanning agents and textile or paper treating materials.
One disadvantage of conventional iron dextran complexes is the fact that it is difficult to obtain stable complexes in colloidal solution with fairly high iron content; say more than 10%, and that as the iron content increases, viscosity of the complex increases rapidly so that at higher iron content the higher viscosity impedes administration by injection and decreases the rate of absorption into animal tissues.